US 7166576 B2
The invention relates to a method for preserving an organ or tissue comprising contacting the organ or tissue with an effective amount of a kallikrein inhibitor and solutions useful for such a method. Also provided is a method for reducing reperfusion injury of an organ during surgery and/or following removal of the organ from a subject comprising placing the organ in an organ storage and preservative solution, wherein the solution comprises a kallikrein inhibitor.
1. A composition for preserving and/or storing an organ comprising a physiologically acceptable ex vivo organ preservation solution containing a polypeptide comprising the amino acid sequence of SEQ ID NO:2 or amino acids 3–60 of SEQ ID NO:2.
2. The composition according to
3. The composition of
This application claims the benefit of U.S. Provisional Application No. 60/407,004, filed Aug. 28, 2002.
The entire teachings of the above application are incorporated herein by reference.
Preservation of the viability of donor organs is an important goal for organ transplantation. Typically the organ to be transplanted must be stored and shipped to the prospective recipient. The ability to prolong the cellular viability of the organ during storage and transportation is very important to the success of the transplant operation. Preservative solutions play an important role in the longevity of the organ. Solutions for organ preservation include those described by Berdyaev et al., U.S. Pat. No. 5,432,053; Belzer et al., U.S. Pat. Nos. 4,798,824, 4,879,283, and 4,873,230; Taylor, U.S. Pat. No. 5,405,742; Dohi et al., U.S. Pat. No. 5,565,317; Stern et al., U.S. Pat. Nos. 5,370,989 and 5,552,267, the contents of which are incorporated herein by reference in their entirety. However, a need exists for improved methods and solutions for organ preservation.
Proteases are involved in a broad range of biological pathways. In particular, serine proteases such as kallikrein, plasmin, elastase, urokinase plasminogen activator, thrombin, human lipoprotein-associated coagulation inhibitor, and coagulation factors such as factors VIIa, IXa, Xa, XIa, and XIIa have been implicated in pathways affecting blood flow, e.g., general and focal ischemia, tumor invasion, fibrinolysis, perioperative blood loss, and inflammation. Inhibitors of specific serine proteases, therefore, have received attention as potential drug targets for various ischemic maladies.
One such inhibitor, aprotinin (also called bovine pancreatic trypsin inhibitor or BPTI), obtained from bovine lung, has been approved in the United States for prophylactic use in reducing perioperative blood loss and the need for transfusion in patients undergoing CPB, e.g., in the course of a coronary artery bypass grafting procedure. Aprotinin is commercially available under the trade name TRASYLOL® (Bayer Corporation Pharmaceutical Division, West Haven, Conn.) and was previously approved for use to treat pancreatitis. The effectiveness of aprotinin is associated with its relatively non-specific abilities to inhibit a variety of serine proteases, including plasma kallikrein, and plasmin. These proteases are important in a number of pathways of the contact activation system (CAS).
CAS is initially activated when whole blood contacts the surface of foreign substrates (e.g., kaolin, glass, dextran sulfate, or damaged bone surfaces). Kallikrein, a serine protease, is a plasma enzyme that initiates the CAS cascade leading to activation of neutrophils, plasmin, coagulation, and various kinins. Kallikrein is secreted as a zymogen (pre-kallikrein) that circulates as an inactive molecule until activated by a proteolytic event early in the contact activation cascade.
However, the use of specific kallikrein inhibitors for organ preservation has not been successfully demonstrated.
This invention is based on the discovery of peptides that inhibit serine proteases, such as, for example, kallikrein, which can successfully be employed to preserve an organ pending transplant. More specifically, the invention provides methods of using kallikrein inhibitors in a method for preserving an organ or tissue and compositions for such use. The invention also relates to methods for reducing, inhibiting or preventing reperfusion injury or damage in an organ or tissue that has been removed from its host and compositions for such use. Preferred kallikrein peptides include those described in U.S. Pat. Nos. 6,333,402 and 6,057,287 to Markland et al., the contents of which are incorporated herein by reference in their entirety.
In a particularly preferred embodiment, the invention is directed to compositions comprising a polypeptide comprising the amino acid sequence:
In a particular embodiment, specific amino acid positions can be the following: Xaa6 can be Ala, Xaa7 can be Phe, Xaa8 can be Lys, Xaa9 can be Ala, Xaa10 can be Asp, Xaa11 can be Asp, Xaa13 can be Pro, Xaa15 can be Arg, Xaa16 can be Ala, Xaa17 can be Ala, Xaa18 can be His, Xaa19 can be Pro, Xaa20 can be Arg, Xaa24 can be Asn, Xaa25 can be Ile, Xaa26 can be Phe, Xaa27 can be Thr, Xaa28 can be Arg, Xaa29 can be Gln, Xaa31 can be Glu, Xaa32 can be Glu, Xaa34 can be Ile, Xaa35 can be Tyr, Xaa39 can be Glu, Xaa41 can be Asn, Xaa42 can be Arg, Xaa44 can be Arg, Xaa46 can be Glu, Xaa47 can be Ser, Xaa48 can be Leu, Xaa49 can be Glu, and/or Xaa50 can be Glu; any of these specific amino acids at these positions can occur individually or in combination with one or more of the amino acids at one or more position otherwise described.
In a particular embodiment, the present invention is directed to a composition comprising a polypeptide as described in SEQ ID NO:1, such that two or more of the following amino acid positions are defined as follows: Xaa10 can be Asp; Xaa11 can be Asp; Xaa13 can be Pro; Xaa15 can be Arg; Xaa16 can be Ala; Xaa17 can be Ala; Xaa18 can be His; Xaa19 can be Pro; Xaa21 can be Trp; Xaa22 can be Phe; Xaa23 can be Phe; Xaa31 can be Glu; Xaa32 can be Glu; Xaa34 can be Ile; Xaa35 can be Tyr; Xaa39 can be Glu; Xaa40 can be Gly; Xaa43 can be Asn; and Xaa45 can be Phe, and methods of using such compositions. In another embodiment, five or more of the following of the following amino acid positions are defined as follows: Xaa10 can be Asp; Xaa11 can be Asp; Xaa13 can be Pro; Xaa15 can be Arg; Xaa16 can be Ala; Xaa17 can be Ala; Xaa18 can be His; Xaa19 can be Pro; Xaa21 can be Trp; Xaa22 can be Phe; Xaa23 can be Phe; Xaa31 can be Glu; Xaa32 can be Glu; Xaa34 can be Ile; Xaa35 can be Tyr; Xaa39 can be Glu; Xaa40 can be Gly; Xaa43 can be Asn; and Xaa45 can be Phe. In another embodiment, 10 or more of the amino acids are defined as follows: Xaa10 can be Asp; Xaa11 can be Asp; Xaa13 can be Pro; Xaa15 can be Arg; Xaa16 can be Ala; Xaa17 can be Ala; Xaa18 can be His; Xaa19 can be Pro; Xaa21 can be Trp; Xaa22 can be Phe; Xaa23 can be Phe; Xaa31 can be Glu; Xaa32 can be Glu; Xaa34 can be Ile; Xaa35 can be Tyr; Xaa39 can be Glu; Xaa40 can be Gly; Xaa43 can be Asn; and Xaa45 can be Phe. In yet another embodiment, 15 or more of the amino acids are defined as follows:
In a particular embodiment, the invention is directed to a composition comprising a polypeptide as defined by SEQ ID NO:1, such that, if present, Xaa3 is Ser, Xaa2 is His, Xaa1 is Met, Xaa56 is Thr, Xaa57 is Arg, and/or Xaa58 is Asp, and methods of using such compositions.
In another embodiment, the invention is directed to a composition comprising a polypeptide comprising the amino acid sequence:
In a particular embodiment, the present invention is directed to a composition comprising a kallikrein binding polypeptide of 53–60 amino acids comprising a Kunitz domain, wherein the Kunitz domain comprises the potential for disulfide bonds between cysteines at positions 5 and 55; 14 and 38; and 30 and 51 (according to amino acid positions corresponding to bovine pancreatic trypsin inhibitor (BPTD), and further comprising:
In a particular embodiment, the present invention is directed to a composition comprising a kallikrein binding polypeptide of 53–60 amino acids comprising a Kunitz domain, wherein the Kunitz domain comprises the potential for disulfide bonds between cysteines at positions 5 and 55; 14 and 38; and 30 and 51 (according to amino acid positions corresponding to bovine pancreatic trypsin inhibitor (BPTI)), and further comprising:
In a particular embodiment, the present invention is directed to a composition comprising a kallikrein binding polypeptide of 53–60 amino acids comprising a Kunitz domain, wherein the Kunitz domain comprises a cysteine at each of positions 5 and 55; 14 and 38; and 30 and 51 (according to amino acid positions corresponding to bovine pancreatic trypsin inhibitor (BPTI), and further comprising:
In a particular embodiment, the Kunitz domain is selected from the group consisting of:
Each of the compositions described herein can be used in the methods of the invention. Further, the compounds described herein can be used in the manufacture of a medicament or composition for the indications or methods described herein.
A description of preferred embodiments of the invention follows.
The invention is based on the discovery of kallikrein inhibitor (KI) polypeptides that inhibit plasma kallikrein with a specificity that permits their use in improved methods of preserving organs and tissues, such as pending a transplantation, and and to corresponding methods. The invention also relates to reducing, inhibiting or preventing reperfusion injury or damage in an organ or tissue that has been removed from its host and compositions therefor.
Polypeptides Useful in the Invention
KI polypeptides useful in the invention comprise Kunitz domain polypeptides. In one embodiment these Kunitz domains are variant forms comprising the looped structure of Kunitz domain 1 of human lipoprotein-associated coagulation inhibitor (LACI) protein. LACI contains three internal, well-defined, peptide loop structures that are paradigm Kunitz domains (Girard, T. et al., 1989. Nature, 338:518–520). The three Kunitz domains of LACI confer the ability to bind and inhibit kallikrein, although not with exceptional affinity. Variants of Kunitz domain 1 of LACI described herein have been screened, isolated and bind kallikrein with enhanced affinity and specificity (see, for example, U.S. Pat. Nos. 5,795,865 and 6,057,287, incorporated herein by reference). An example of a preferred polypeptide useful in the invention has the amino acid sequence defined by amino acids 3–60 of SEQ ID NO:2.
Kallikrein binding polypeptides can be used to target therapeutic or diagnostic molecules to kallikrein in, for example, organ tissue, cells, or whole organisms. Such methods of targeted delivery for therapeutic or diagnostic purposes would be known to one of skill in the art. For example, targeted kallikrein binding polypeptides could be used by one of skill in the art to identify an organ that has been damaged by the effects of kallikrien, or kallikrein can be targeted for the effects of a particular therapeutic agent using kallikrein binding polypeptides of the invention.
Every polypeptide useful in the invention binds kallikrein. In preferred embodiments, the polypeptides are kallikrein inhibitors (KI) as determined using kallikrein binding and inhibition assays known in the art. The enhanced affinity and specificity for kallikrein of the variant Kunitz domain polypeptides described herein provides the basis for their use in CPB and especially CABG surgical procedures to prevent or reduce perioperative blood loss and/or SIR in patients undergoing such procedures. The KI polypeptides used in the invention can have or comprise the amino acid sequence of a variant Kunitz domain polypeptide originally isolated by screening phage display libraries for the ability to bind kallikrein.
KI polypeptides useful in the methods and compositions of the invention comprise a Kunitz domain polypeptide comprising the amino acid sequence:
Peptides defined according to SEQ ID NO:1 form a set of polypeptides that bind to and inhibit kallikrein. The diversity of the KI's is increased as the number of variable positions in the peptide sequence is increased or as the number of amino acids possible at a variable position increases. For example, in a preferred embodiment of the invention, a KI polypeptide useful in the methods and compositions of the invention has the following variable positions: Xaa11 can be Asp, Gly, Ser or Val; Xaa13 can be Pro, Arg, His or Asn; Xaa15 can be Arg or Lys; Xaa16 can be Ala or Gly; Xaa17 can be Ala, Asn, Ser or Ile; Xaa18 can be His, Leu or Gln; Xaa19 can be Pro, Gln or Leu; Xaa21 can be Trp or Phe; Xaa31 is Glu; Xaa32 can be Glu or Gln; Xaa34 can be Ile, Thr or Ser; Xaa35 is Tyr; and Xaa39 can be Glu, Gly or Ala.
A more specific embodiment of the claimed invention is defined by the following amino acids at variable positions: Xaa10 is Asp; Xaa11 is Asp; Xaa13 can be Pro or Arg; Xaa15 is Arg; Xaa16 can be Ala or Gly; Xaa17 is Ala; Xaa18 is His; Xaa19 is Pro; Xaa21 is Trp; Xaa31 is Glu; Xaa32 is Glu; Xaa34 can be Ile or Ser; Xaa35 is Tyr; and Xaa39 is Gly.
Also encompassed within the scope of the invention are peptides that comprise portions of the polypeptides described herein. For example, polypeptides could comprise binding domains for specific kallikrein epitopes. Such fragments of the polypeptides described herein would also be encompassed.
KI polypeptides useful in the methods and compositions described herein comprise a Kunitz domain. A subset of the sequences encompassed by SEQ ID NO:1 are described by the following (where not indicated, “Xaa” refers to the same set of amino acids that are allowed for SEQ ID NO:1):
Other KI polypeptides useful in the present invention include:
These sequences are summarized in the following Table 1.
The polypeptides useful in the methods and compositions described herein may be made synthetically using any standard polypeptide synthesis protocol and equipment. For example, the stepwise synthesis of a KI polypeptide described herein may be carried out by the removal of an amino (N) terminal-protecting group from an initial (i.e., carboxy-terminal) amino acid, and coupling thereto of the carboxyl end of the next amino acid in the sequence of the polypeptide. This amino acid is also suitably protected. The carboxyl group of the incoming amino acid can be activated to react with the N-terminus of the bound amino acid by formation into a reactive group such as formation into a carbodiimide, a symmetric acid anhydride, or an “active ester” group such as hydroxybenzotriazole or pentafluorophenyl esters. Preferred solid-phase peptide synthesis methods include the BOC method, which utilizes tert-butyloxycarbonyl as the a-amino protecting group, and the FMOC method, which utilizes 9-fluorenylmethloxycarbonyl to protect the a-amino of the amino acid residues. Both methods are well known to those of skill in the art (Stewart, J. and Young, J., Solid-Phase Peptide Synthesis (W. H. Freeman Co., San Francisco 1989); Merrifield, J., 1963. Am. Chem. Soc., 85:2149–2154; Bodanszky, M. and Bodanszky, A., The Practice of Peptide Synthesis (Springer-Verlag, New York 1984), the entire teachings of these references is incorporated herein by reference). If desired, additional amino- and/or carboxy-terminal amino acids may be designed into the amino acid sequence and added during polypeptide synthesis.
Alternatively, Kunitz domain polypeptides and KI polypeptides useful in the compositions and methods of the invention may be produced by recombinant methods using any of a number of cells and corresponding expression vectors, including but not limited to bacterial expression vectors, yeast expression vectors, baculovirus expression vectors, mammalian viral expression vectors, and the like. Kunitz domain polypeptides and KI polypeptides useful in the compositions and methods of the invention may also be produced transgenically using nucleic acid molecules comprising a coding sequence for a Kunitz domain or KI polypeptide described herein, wherein the nucleic acid molecule can be integrated into and expressed from the genome of a host animal using transgenic methods available in the art. In some cases, it may be necessary or advantageous to fuse the coding sequence for a Kunitz domain polypeptide or a KI polypeptide comprising the Kunitz domain to another coding sequence in an expression vector to form a fusion polypeptide that is readily expressed in a host cell. Preferably, the host cell that expresses such a fusion polypeptide also processes the fusion polypeptide to yield a Kunitz domain or KI polypeptide useful in the invention that contains only the desired amino acid sequence. Obviously, if any other amino acid(s) remain attached to the expressed Kunitz domain or KI polypeptide, such additional amino acid(s) should not diminish the kallikrein binding and/or kallikrein inhibitory activity of the Kunitz domain or KI polypeptide so as to preclude use of the polypeptide in the methods or compositions of the invention.
A preferred recombinant expression system for producing KI polypeptides useful in the methods and compositions described herein is a yeast expression vector, which permits a nucleic acid sequence encoding the amino acid sequence for a KI polypeptide or Kunitz domain polypeptide to be linked in the same reading frame with a nucleotide sequence encoding the mata prepro leader peptide sequence of Saccharomyces cerevisiae, which in turn is under the control of an operable yeast promoter. The resulting recombinant yeast expression plasmid may then be transformed by standard methods into the cells of an appropriate, compatible yeast host, which cells are able to express the recombinant protein from the recombinant yeast expression vector. Preferably, a host yeast cell transformed with such a recombinant expression vector is also able to process the fusion protein to provide an active KI polypeptide useful in the methods and compositions of the invention. A preferred yeast host for producing recombinant Kunitz domain polypeptides and KI polypeptides comprising such Kunitz domains is Pichia pastoris.
As noted above, KI polypeptides that are useful in the methods and compositions described herein may comprise a Kunitz domain polypeptide described herein. Some KI polypeptides may have an additional flanking sequence, preferably of one to six amino acids in length, at the amino and/or carboxy-terminal end, provided such additional amino acids do not significantly diminish kallikrein binding affinity or kallikrein inhibition activity so as to preclude use in the methods and compositions described herein. Such additional amino acids may be deliberately added to express a KI polypeptide in a particular recombinant host cell or may be added to provide an additional function, e.g., to provide a peptide to link the KI polypeptide to another molecule or to provide an affinity moiety that facilitates purification of the polypeptide. Preferably, the additional amino acid(s) do not include cysteine, which could interfere with the disulfide bonds of the Kunitz domain. Native examples of Kunitz domains exhibit disulfide bonds, e.g., BPTI contains disulfide bonds between cysteine residues at amino acid positions 5 and 55; 14 and 38; and 30 and 51
An example of a preferred Kunitz domain polypeptide useful in the methods and compositions of the invention has the amino acid sequence of residues 3–60 of SEQ ID NO:2. When expressed and processed in a yeast fusion protein expression system (e.g., based on the integrating expression plasmid pHIL-D2), such a Kunitz domain polypeptide retains an additional amino terminal Glu-Ala dipeptide from the fusion with the mata prepro leader peptide sequence of S. cerevisiae. When secreted from the yeast host cell, most of the leader peptide is processed from the fusion protein to yield a functional KI polypeptide (also referred to as “PEP-1” or “DX88”) having the amino acid sequence of SEQ ID NO:2 (see boxed region in
Particularly preferred KI polypeptides useful in the methods and compositions described herein have a binding affinity for kallikrein that is on the order of 1000 times higher than that of aprotinin, which is currently approved for use in CABG procedures to reduce blood loss. The surprisingly high binding affinities of such KI polypeptides described herein indicate that such KI polypeptides exhibit a high degree of specificity for kallikrein to the exclusion of other molecular targets (see Table 1, below). Thus, use of such polypeptides according to the invention reduces much of the speculation as to the possible therapeutic targets. The lower degree of specificity exhibited by, for example, aprotinin, leads to possible pleiotropic side effects and ambiguity as to its therapeutic mechanism.
The polypeptides defined by, for example, SEQ ID NO:1 contain invariant positions, e.g., positions 5, 14, 30, 51 and 55 can be Cys only. Other positions such as, for example, positions 6, 7, 8, 9, 20, 24, 25, 26, 27, 28, 29, 41, 42, 44, 46, 47, 48, 49, 50, 52, 53 and 54 can be any amino acid (including non-naturally occurring amino acids). In a particularly preferred embodiment, one or more amino acids correspond to that of a native sequence (e.g., LACI (SEQ ID NOS:32–34)). In a preferred embodiment, at least one variable position is different from that of the native sequence. In yet another preferred embodiment, the amino acids can each be individually or collectively substituted by a conservative or non-conservative amino acid substitution. Conservative amino acid substitutions replace an amino acid with another amino acid of similar chemical structure and may have no affect on protein function. Non-conservative amino acid substitutions replace an amino acid with another amino acid of dissimilar chemical structure. Examples of conserved amino acid substitutions include, for example, Asn->Asp, Arg->Lys and Ser->Thr. In a preferred embodiment, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,20 and/or 21 of these amino acids can be independently or collectively, in any combination, selected to correspond to the corresponding position of SEQ ID NO:2.
Other positions, for example, positions 10, 11, 13, 15, 16, 17, 18, 19, 21, 22, 23, 31, 32, 34, 35, 39, 40, 43 and 45, can be any of a selected set of amino acids. Thus SEQ ID NO:1 defines a set of possible sequences. Each member of this set contains, for example, a cysteine at positions 5, 14, 30, 51 and 55, and any one of a specific set of amino acids at positions 10, 11, 13, 15, 16, 17, 18, 19, 221, 22, 23, 31, 32, 34, 35, 39, 40, 43 and 45. In a preferred embodiment, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 and/or 19 of these amino acids can be independently or collectively, in any combination, selected to correspond to the corresponding position of SEQ ID NO:2. The peptide preferably has at least 80%, at least 85%, at least 90% or at least 95% identity to SEQ ID NO:2.
Methods and Compositions
The present invention is directed to methods for preserving organs and tissues comprising contacting the organ or tissue with a preservative solution comprising a kallikrein inhibitor, such as those described herein. The invention also relates to reducing, inhibiting or preventing reperfusion injury or damage in an organ or tissue that has been removed from its host comprising contacting the organ or tissue with a kallikrein inhibitor. The preservative solutions of the invention can be used to preserve and/or protect organ tissue, or whole organs, when said organs or tissue are brought into contact with the solution. A specific embodiment of the invention is for the preservation of a human heart, or human myocardial tissue. Another embodiment of the invention is for the preservation of a human lung or human lung tissue. Other organs, or parts thereof, that can be preserved according to the invention include kidney, liver, endothelial tissue, intestinal tissue, vascular tissue (e.g., an aorta graft), skin, and pancreas. The invention contemplates the use of the solutions to preserve mammalian tissue, organs or portion thereof. In addition, the solutions can be used to facilitate transplantation of organs, e.g., by perfusion of the organ or tissue during the transplantation procedure. The solution can also be used as a cardioplegia solution in cardiac surgery. Preferably, the organ or portion thereof, is maintained in the appropriate solution at all times, particularly prior to the transplant procedure.
The solutions of the invention can be used to maintain viability of the organ or tissue during storage, transplantation or other surgery. The invention includes a method of storing tissue or organs comprising contacting said tissue, organ or part thereof, with the solution of the invention, such that the in vivo and/or in vitro viability is prolonged. The solutions permit maintenance of viability of heart or lung tissue for up to 24 hours or more. Use of the solutions of the invention results in improved organ viability.
Alternatively or in addition, once removed from the donor, the organ or living tissue may be placed in a preservation solution containing the inhibitor. In addition, the kallikrein inhibitor is also preferably administered to the transplant recipient just prior to, or concommitant with, transplantation. In all cases, the inhibitor also can be administered directly to the tissue at risk, as by injection to the tissue, or it may be provided systemically, either by oral or parenteral administration, using any of the methods and formulations described herein and/or known in the art.
In one embodiment, any commercially available preservation solution may be used to advantage. Examples of such solutions include the Belzer UW solution sold under the trademark VIASPAN, described in U.S. Pat. Nos. 4,798,824, 4,873,230, 4,879,283, which are hereby incorporated by reference.
The preservation solution and perfusate composition described in the aforementioned patents includes, but is not limited to, the following:
The solution is brought to pH 7.4 at room temperature with NaOH. The final concentrations are Na=30.±0.5 mM, K+=120±5 mM, mOsm/liter=320±5. Bactrim=trimethoprim (16 mg/mL) and sulfamethoxazole (80 mg/mL). The hydroxyethyl starch can be present in the range of from about 3 to about 8%.
This solution typically provides for a 72 hour preservation of the pancreas, 48 hour preservation for the kidney and at least 24 hour preservation for the liver. U.S. Pat. No. 5,145,771, incorporated herein by reference, described the organ preservation solution known as the “Carolina Solution,” which is also useful in the present invention. The rinse or preservation solution composition described in the aforementioned patent includes, but is not limited to, the components in about the concentration ranges set forth in Table 3 below.
One specific embodiment is prepared with the components in the amounts set forth in Table 4 below in accordance with the instructions set forth below.
In one embodiment this solution can be prepared as follows: using a 500 mL volumetric flask, measure 500 mL of 10% (weight/volume) hydroxyethyl starch solution and pour into a 1 L beaker. Add 400 mL of double distilled water and stir vigorously using a magnetic stir bar. Add the rest of the components one at a time. After all components are added, adjust the pH to 6.5 with 1–2 mL 5N NaOH. The solution should be stirred for at least thirty minutes. Transfer the solution to a 1 L volumetric flask and bring to 1 L final volume. Filter to remove any undissolved particles.
Still another embodiment is exemplified by Table 5 below.
A composition according to Table 5 above may optionally include one, several, or all of the further ingredients specified in Table 3 above. Preferably, the composition includes at least one antioxidant. Thus, one specific embodiment of a composition is set forth in Table 6 below:
Preferred compositions may further comprise one or more pharmaceutically acceptable buffers, carriers, antioxidants, protease inhibitors, or other anti-ischemia agents.
Compositions useful in the methods of the invention comprise any of the Kunitz domain polypeptides or KI polypeptides comprising such Kunitz domain polypeptides described herein. Particularly preferred are RI polypeptides comprising a Kunitz domain polypeptide having a 58-amino acid sequence of amino acids 3–60 of SEQ ID NO:2. An example of particularly preferred KI polypeptide useful in the methods and compositions of the invention is the PEP-1 KI polypeptide having the 60-amino acid sequence of SEQ ID NO:2. A nucleotide sequence encoding the amino acid sequence of SEQ ID NO:2 is provided in SEQ ID NO:3 (see, e.g., nucleotides 309–488 in
Concentration Considerations for KI Polypeptides
Several considerations regarding dosing with a KI polypeptide in methods of the invention may be illustrated by way of example with the representative PEP-1 KI polypeptide of the invention having the amino sequence of SEQ ID NO:2 (molecular weight of 7,054 Daltons).
Table 7, below, provides a comparison of the affinity (Ki,app) of the PEP-1 KI polypeptide for kallikrein and eleven other known plasma proteases.
Clearly, the PEP-1 KI polypeptide is highly specific for human plasma kallikrein. Furthermore, the affinity (Ki,app) of PEP-1 for kallikrein is 1000 times higher than the affinity of aprotinin for kallikrein: the Ki,app of PEP-1 for kallikrein is about 44 pM (Table 1), whereas the Ki,app of aprotinin for kallikrein is 30,000 pM. Thus, a dose of PEP-1 could be approximately 1000 times lower than that used for aprotinin on a per mole basis. However, consideration of several other factors may provide a more accurate estimation of the dose of PEP-1 required in practice. Such factors include the amount of kallikrein activated upon organ removal from a particular patient, and will be recognized by the skilled artisan.
The invention will be further described with reference to the following non-limiting examples. The teachings of all the patents, patent applications and all other publications and websites cited herein are incorporated by reference in their entirety.
A KIT polypeptide useful in the compositions and methods of the invention was identified as a kallikrein binding polypeptide displayed on a recombinant phage from a phage display library. PEP-1 has the following amino acid sequence: Glu Ala Met His Ser Phe Cys Ala Phe Lys Ala Asp Asp Gly Pro Cys Arg Ala Ala His Pro Arg Trp Phe Phe Asn Ile Phe Thr Arg Gln Cys Glu Glu Phe Ile Tyr Gly Gly Cys Glu Gly Asn Gln Asn Arg Phe Glu Ser Leu Glu Glu Cys Lys Lys Met Cys Thr Arg Asp (SEQ ID NO:2). The molecular weight of PEP-1 is 7,054 Daltons.
The nucleotide sequence (SEQ ID NO:3) encoding the PEP-1 amino acid sequence (SEQ ID NO:2) was derived from a peptide that was isolated and sequenced by standard methods determined from the recombinant phage DNA. PEP-1 was produced in amounts useful for further characterization as a recombinant protein in His4 phenotype host cells of yeast strain Pichia pastoris.
The initial plasmid, pHIL-D2, is ampicillin resistant and contains a wild-type allele of His4 from P. pastoris. The final DNA sequence comprising the coding sequence for the mata Prepro-PEP-1 fusion protein in the recombinant expression plasmid pPIC-K503 is shown in
The ligation products were used to transform Escherichia coli strain XL1 Blue. A PCR assay was used to screen E. coli transformants for the desired plasmid construct. DNA from cell extracts was amplified by PCR using primers containing the 5′ AOX1 and 3′ AOX1 sequences (see above and
Spheroplasts of P. pastoris GS115 having the His4− phenotype were transformed with the expression plasmid pPIC-K503 (above) following linearization of the plasmid at the SacI site and homologous recombination of the plasmid DNA into the host 5′ AOX1 locus. The phenotype of the production strain is His4+. The entire plasmid was inserted into the 5′ AOX1 genomic sequence of the yeast.
Isolates from the transformation were screened for growth in the absence of exogenous histidine with methanol as the sole carbon source. Greater than 95% of the transformants retained the wild-type ability to grow with methanol as the sole carbon source, thereby demonstrating that the plasmid had been inserted into the host genome by homologous recombination rather than transplacement. These transformants did not require exogenous histidine for growth, thereby demonstrating that the plasmid had integrated into the host genome. Selected colonies were cloned. Small culture expression studies were performed to identify clones secreting the highest levels of active PEP-1 into the culture medium. PEP-1 secretion levels in clarified culture supernatant solutions were quantified for PEP-1 levels by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and evaluated for kallikrein inhibition. A yeast clone was selected for PEP-1 production based on its high level of PEP-1 expression among cultures sampled.
Master and working cell banks of P. pastoris producing PEP-1 were prepared commercially (MDS Pharma Services, Bothell, Wash.). A standard production of PEP-1 in yeast comprised three steps as follows: (1) preparation of the seed culture, (2) fermentation, and (3) recovery of the culture.
The seed culture step consisted of the inoculation of six flasks (300 mL each) containing sterile inoculum broth (yeast nitrogen base, potassium phosphate, and glycerol, pH=5) with the contents of a single vial of a working cell bank of P. pastoris producing PEP-1. Flasks were inoculated in an orbital shaker (300 rpm) for approximately 13 hours at 30° C.±2° C.
Fermentations were performed in a closed 100 liter Braun fermenter filled with sterile broth. Each fermentation was initiated with the transfer of the contents of the six seed culture flasks to the fermenter. After approximately 24 hours, the glycerol in the fermenter became exhausted and additional glycerol was added for approximately 8 additional hours.
A mixed feed phase, which lasted approximately 83 hours, was then initiated by the addition of a glycerol and methanol feed. At the end of this time, the fermentation was terminated, and the fermenter contents were diluted with purified water. The purification and processing of PEP-1 consisted of five steps as follows: (1) expanded bed chromatography, (2) cation exchange chromatography, (3) hydrophobic interaction chromatography (HIC), (4) ultrafiltration and diafiltration, and (5) final filtration and packaging.
The initial purification step consisted of expanded bed chromatography. The diluted fermenter culture was applied to the equilibrated column packed with Streamline SP resin (Amersham Pharmacia Streamline 200 chromatography column, Amersham Pharmacia, Piscataway, N.J.). The column was then washed (50 mM acetic acid, pH=3.0−3.5) in an up-flow mode to flush the yeast cells from the expanded bed. The top adaptor was raised above the expanded bed enhance washing. The flow was stopped and the bed was allowed to settle. The adaptor was moved down so that it was slightly above the settled bed. The direction of the flow was reversed. The effluent was collected. Washing was continued in a downward mode using 50 mM sodium acetate, pH 4.0. The effluent was collected. PEP-1 was eluted from the column using 50 mM sodium acetate, pH 6.0. The eluate was collected in a 50 liter container. The eluate was then filtered through a 0.22 m filter into a clean container located in the purification site. Additional samples were collected for the determination of PEP-1 concentration. A cation exchange chromatography step was then performed using the filtered eluate from the expanded bed column. PEP-1 was eluted from the column using 15 mM trisodium citrate, pH 6.2.
Additional proteins were removed from the PEP-1 preparation by hydrophobic interaction chromatography (HIC). Prior to HIC, the eluate from the cation exchange column was diluted with ammonium sulfate. The eluate was applied to the column, and the PEP-1 was eluted using ammonium sulfate (0.572 M) in potassium phosphate (100 mM), pH 7.0. The eluate was collected in fractions based on A280 values. All fractions were collected into sterile, pre-weighed PETG bottles.
Selected fractions were pooled into a clean container. The pool was concentrated by ultrafiltration. The concentrated PEP-1 preparation was immediately diafiltered against ten volumes of PBS, pH 7.0.
A final filtration step was performed prior to packaging in order to minimize the bioburden in the bulk PEP-1. The bulk solution was filtered through a 0.22 m filter and collected into a sterile, pre-weighed PETG bottle. A sample was removed for lot release testing. The remainder of the bulk was dispensed aseptically into sterile PETG bottles and stored at −20° C.
A kinetic test was used to measure inhibitory activity of KI polypeptides, such as PEP-1. The kinetic assay measures fluorescence following kallikrein-mediated cleavage of a substrate, prolylphenylalanylarginyl amino methyl coumarin. A known amount of kallikrein was incubated with a serially diluted KI polypeptide reference standard or serially diluted KI polypeptide test samples, in a suitable reaction buffer on a microtiter plate. Each sample was run in triplicate. The substrate solution was added, and the plate read immediately using an excitation wavelength of 360 nm and an emission wavelength of 460 nm. At least two each of the reference standard and sample curves were required to have an R-squared value of 0.95 to be considered valid.
HUVEC at confluence were washed in PBS and further incubated at 4 degrees for 24–48 hours in a serum free medium (SFM). After cold storage, cells were washed several times with PBS, and kallikrein (0.125 U) and the specific kallikrein substrate S2302 were added to the cells. Changes in optical density were recorded. For light microscopy evaluation of cell-bound PEP-1, after cold storage, HUVEC were treated with PEP-1, formalin fixed and treated with rabbit anti-PEP-1 and peroxidase conjugated anti-rabbit IgG. The ability of HUVEC to produce kallikrein was also evaluated on cell surface and in the supernatants of cells maintained at 37° C. Kallikrein activity was 380±19 A.U. in supernatants of HUVEC maintained at 37° C.; no activity was measurable on the surface of the same cells. At light microscopy evaluation there was significant binding of PEP-1 to the surface of HUVEC cold treated for 24 hours. The maximum of the binding was obtained by incubating cells in presence of PEP-1 (5 mg/ml). Cell-bound PEP-1 retained the ability to inhibit exogenous kallikrein. These results indicate that PEP-1 binds to endothelial cells, maintaining its kallikrein inhibitory activity. Therefore it can be used to detect and modulate kinin-mediated damage on the vascular surface.
While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.